More global banks are being investigated for the alleged financial market manipulation that led to fines of $US453 million ($A450.8 million) against Barclays Bank, British Treasury chief George Osborne says.
US and British regulators have fined Barclays for manipulating the interest rate - the London interbank offered rate - to its advantage between 2005 and 2009. The rate is used to price mortgages and consumer loans.
Mr Osborne says Barclays is not the only bank involved in market fixing. There are investigations in several countries involving, among others, Citigroup in the US, Switzerland's UBS and Britain's HSBC and Royal Bank of Scotland.
The banks' share price fell sharply on Thursday as investors expected hefty fines and tighter regulation. Barclays shares closed down 15.5 per cent, RBS 11.5 per cent, HSBC 2.6 per cent and Lloyds Banking Group 3.9 per cent.
UBS shares were down 3.8 per cent in afternoon trading, and Citigroup shares were down 0.1 per cent.
Britain's Financial Services Authority cited evidence Barclays traders were in touch with people in other banks.
"Banks were clearly acting in concert," said Andrew Tyrie, Treasury Committee chairman in the House of Commons. "I fear it's not going to be the end of the story, that we are going to find that other banks have been involved."
Tyrie said his committee would summon Barclays chief Bob Diamond to explain what happened.
The massive fines are unlikely to be the end of the pain for Barclays. The cost of lawsuits related to the LIBOR scandal will likely be bigger, said Sandy Chen, banking analyst at Cenkos Securities.
"Since Royal Bank of Scotland, HSBC and Lloyds Banking Group have also been named in lawsuits, we expect they will also face significant fines and damages. We are pencilling in multi-year provisions that could run into the billions," Chen said.